Gastrulation

Question 0

At least half of all embryos are spontaneously aborted due to ___. Approximately __ of live births suffer from congenital defects. These results in personal suffering & huge costs to medical care systems.

Answer 0

developmental defects; 4%

Question 1

Understanding developmental processes will ultimately lead to preventative strategies.

Answer 1

yup!

Question 2

Embryonic cells divide about every ___ hours

Answer 2

16-24. Reductive division.

Question 3

As the morula divides, some cells find themselves on the inside. These cells begin to express different genes including ____. ___ is an important marker of __ stem cells

Answer 3

Oct4; Oct4; pluripotent

Question 4

As the blastula forms, the cells separate into 2 populations - the ___ & ___ layer

Answer 4

inner cell mass & trophoblast layer

Question 5

Initially the ICM is an ____ of cells.

Answer 5

unorganized cluster of cells

Question 6

The cells of ICM then separate into 2 layers the ___ & ___. Together, these 2 layers comprise the ___

Answer 6

epiblast & hypoblast; embryonic disk

Question 7

How many days after fertilization does the ICM form 2 layers?

Answer 7

6-7 days - around time of implantation

Question 8

After how many days after fertilization does the ICM cells express Oct4?

Answer 8

about 5 days after fertilization

Question 9

The epiblast cells are high ___ in appearance. All cells of embryo itself will arise from the ___ layer

Answer 9

columnar; epiblast

Question 10

What does the hypoblast form?

Answer 10

the supporting layer; forms yolk sac wall

Question 11

The epiblast separates into 2 layers to form the ___. Only epiblast cells in contact with __ will form embryonic tissues.

Answer 11

amniotic cavity; hypoblast

Question 12

The amniotic membrane is an ___ tissue. The amniotic fluid in the cavity protects the embryo

Answer 12

extraembyonic tissue

Question 13

How many days after fertilization does the epiblast separate?

Answer 13

9 days after fertilization

Question 14

From 7-14 days, the embryo undergoes rapid ___

Answer 14

cell division

Question 15

The disk changes from roughly circular to ___, broader at __ end.

Answer 15

ovoid; cranial end

Question 16

By 16 days the disk is approximately __mm x ___mm in size

Answer 16

1x1.5mm

Question 17

Despite the undifferentiated appearance of the embryonic disk, a number of signaling events have already occurred. These will later distinguish specific regions of the embryo

Answer 17

primitive streak forms

Question 18

How many cells are present in the mature human body?

Answer 18

1cm^3 = 10^9 cells

Question 19

What is gastrulation?

Answer 19

process by which 3 embryonic germ layers are formed. Ectoderm, mestoderm & endoderm

Question 20

Through physical movements of gastrulation, original epiblast tissue is divided into 3 different ___

Answer 20

tissue layers

Question 21

Gastrulation commences about __ days after fertilization

Answer 21

14

Question 22

The primitive streak is first visible at the ___ end & then extends more ___

Answer 22

caudal; cranially

Question 23

The streak marks the position where epiblast cells have migrated towards the ___ & then ___. These migratory cells are called ____. ___ is a rather general term for loosely associated & migratory cells.

Answer 23

midline & then ingressed; mesenchyme; mesenchyme

This is an example of EMT (epithelial to mesenchymal transition - metastasis?)

Question 24

Epiblast becomes the ___ & the migratory cells displacing the hypoblast becomes the ___

Answer 24

skin - ectoderm

gut - mesoderm

Question 25

What are the migratory cells falling towards the hypoblast?

Answer 25

because cell loses cell-cell adhesion & therefore drops down & displaces the hypoblast

Question 26

The first cells to ingres insert into hypoblast layer & displace it. These cells will form the embryonic __

Answer 26

endoderm

Question 27

From top to bottom, what are the layers?

Answer 27

epiblast (future ectoderm), mesenchyme (future mesoderm) & hypoblast (future endoderm)

Question 28

The mesoderm cells migrate both ___ & ____ until they occupy almost* the entire middle layer of the embryo

Answer 28

laterally & cranially

Question 29

What is the future mouth & future anus called?

Answer 29

oral membrane & cloacal membrane

Question 30

The oral & cloacal membrane will not contain ___

Answer 30

mesoderm

Question 31

What is a notochord? It is also the center for ___ (by GF) to adjacent tissues. The notochord is later incorporated into the ___. The final remamnant of the notochord is the ____ of the intervertebral disk.

Answer 31

transient embryonic structure that acts as temporary spine for embryo

signaling by GF to adjacent tissues

backbone

nucleus pulplosis

Question 32

Humans are in what phylum?

Answer 32

chordata - chords!!

Question 33

As gastrulation proceeds the primitive streak regresses ___. It lays down more ___ as it regresses. The streak disappears by about day ___. If the streak cells don’t disappear, they may give rise to highly invasive class of tumors =

Answer 33

caudally; notochord; 30; sacral teratoma!

Question 34

What is ectoderm, mesoderm & endoderm?

Answer 34

Ectoderm - outer layer of skin (epidermis) & neural tissues

Mesoderm - skeletal & smooth muscle, heart & blood vessels, blood, bones, dermis of skin. Supporting tissue b/w skin & gut tube

Endoderm - visceral organs including gut tube, bladder, liver, pancreas & lungs

Question 35

Cells in the ICM are ___. They can develop into ____ different type of cell in the body. This has been confirmed many times with experimental animals.

Answer 35

totipotent; EVERY

Question 36

It is now possible to grow human ICM cells indefinitely in culture. They’re called ___

Answer 36

human ES cells (hESCs)

In addition to GF, the culture medium contains # of factors that inhibit differentiation

Question 37

What is iPS cells?

Answer 37

induced pluripotent cells